1. Field of the Invention
This invention relates to an operation inputting apparatus which includes a stick type operation member, and more particularly to an operation inputting apparatus such as a computer keyboard apparatus which eliminates any possible disadvantage encountered when a stick type operation member is operated with an excessively high operating force as well as an operation inputting apparatus which minimizes a dispersion in detection output value of a detection sensor used for a stick type pressure sensor and a detection error arising from an influence of an environmental circumstance, a disturbance or the like.
2. Description of the Related Art
Conventionally, various keyboard apparatus are known including a keyboard apparatus of the type which only includes several operation keys arranged in a predetermined order on an operation section and another keyboard apparatus of the type which includes such operation keys and a stick type operation member (stick pointer) located at a predetermined location among the operation keys.
A stick type operation member (stick pointer) for use with a keyboard apparatus includes a total of four strain gauges each on each of the opposite sides of a root portion thereof in a transverse direction (X-axis direction) and a depthwise direction (Y-axis direction). The paired strain gauges in each of the transverse and depthwise directions are connected in series across a dc power source, and detection outputs in the transverse direction and the depthwise direction are extracted from connection points of the paired strain gauges. Then, if an operator pushes, with a fingertip thereof, at an end of the stick type operation member to move in a desired direction, then a load force applied upon such movement acts upon the strain gauges in the two different directions so that the resistance values of the strain gauges are varied. Consequently, if the variations of the resistance values are detected as voltage variations in the individual directions and the detection outputs are read, then operation data representative of the load force to the end of the stick type operation member can be obtained. Then, the operation data representative of the load force are digitized and processed suitably in the keyboard apparatus and then transmitted to a main unit such as a personal computer to which the keyboard apparatus is connected.
In the meantime, in the main unit, when the operation data representative of the load force are supplied to a display section, they act to move a cursor in the display section. In this instance, the direction of movement of the cursor is determined in accordance with the direction of the load (pressing) force applied to the stick type operation member while the speed of movement of the cursor is determined in accordance with the magnitude of the load (pressing) force applied to the stick type operation member.
In the known keyboard apparatus of the type which includes a stick type operation member (stick pointer), if a key operator pushes (operates) the end of the stick type operation member to move in a desired direction, then the load (pressing) force applied upon such movement (operation) acts upon the strain gauges in the different directions so that the resistance values of the strain gauges are varied, and the variations of the resistance values are detected as voltage variations. If the key operator removes the load (pressing) force applied to the end of the stick type operation member, then the resistance values of the strain gauges must restore to their original values exhibited prior to their variations and also the detection outputs extracted from the connection points between the paired strain gauges must restore their original values exhibited prior to the variations.
With an actual stick type operation member(stick pointer), however, since inertia of the stick type operation member itself and/or a residual component of a displacement arising from adhesion of a bonding agent or the like are present, even if the load (pressing) force applied to move the stick type operation member by pushing operation of the same is removed, the stick type operation member will not immediately restore its original condition exhibited prior to such movement but will restore its original condition exhibited prior to the movement after lapse of a short time. Also the detection outputs extracted from the connection points between the paired strain gauges do not immediately restore their original conditions exhibited prior to the variations, but the variation residual component gradually attenuates until it decreases finally to zero. Particularly if a high load (pressing) force is applied when the stick type operation member is pushed (operated) to move, the displacement residual component is produced notably.
FIGS. 7(a) and 7(b) illustrate a relationship between the operation condition of the stick type operation member (stick pointer) and the load detection output obtained by the operation, and in particular, FIG. 7(a) illustrates the operation condition while FIG. 7(b) shows the actual load detection output.
In FIGS. 7(a) and 7(b), the axis of ordinate indicates the load level and the axis of abscissa indicates time.
When the stick type operation member is operated for a fixed period of time, if a load (pressing) force higher than a certain level is applied to operate the stick type operation member as seen in FIG. 7(a), then even if the thus applied load (pressing) force is removed after lapse of the fixed period of time, the load detection output does not immediately restore its original level exhibited prior to the variation, but returns to its original level after a process of displacement which decreases gradually.
Meanwhile, in the known keyboard apparatus of the type which includes a stick type operation member, when the cursor on the display section of the main unit is moved by a pushing operation of the stick type operation member, since the speed of movement of the cursor increases linearly in proportion to the load (pressing) force applied upon the operation of the stick type operation member, if a key operator wants to take a great amount of movement of the cursor, then if the key operator tries to achieve the movement of the cursor in a comparatively short time, then a high load (pressing) force must be applied continuously to the stick type operation member. Besides, when such movement of the cursor by a great amount is performed successively, the movement of the cursor becomes considerably slow, resulting in a problem that the operator may be irritated very much.
Further, there is a different problem in that, when the end of the stick type operation member is pushed to move, since the variation in resistance value caused by the pressing force applied to each pressure detection sensor (strain gauge) is very small, where the dispersion in initial resistance value among the paired pressure detection sensors (strain gauges) provided for each of the two perpendicular directions is great, fine variations of the resistance values obtained by the pressure detection sensors (strain gauges) cannot be read accurately.
Further, in the known keyboard apparatus having a stick type operation member, when fine detection outputs obtained from the paired pressure detection sensors (strain gauges) provided for the two different directions are amplified, a level variation is produced in the fine detection outputs by a variation of the power source voltage, a variation in ambient temperature, application of external noise or the like. Consequently, there is a further problem in that a fine variation in resistance value of each of the pressure detection sensors (strain gauges) cannot be read accurately.